Routing 1 GBit/s WAN speed already requires a lot of CPU power, limiting your options to a rather small set of devices. SQM increases this problem significantly, pointing quite heavily at x86_64 (~core i5). Four 1000BASE-T ethernet ports break the camel's back, leaving you with e.g. the aforementioned qotom series or the odroid h2+ && H2 Net Card - or something in that general direction.
Next stop, a good (OpenWrt supported-) router to be used as dedicated access point(s).